In this paper, a boundary value problem formulated previously by N. Swaminathan, J. Qu, Y. Sun, Phil. Mag. 2006 (this volume) is solved to obtain the defect, stress distributions in a planar electrolyte in solid oxide fuel cells. It is found that analytical solutions from the coupled theory reduce to the known results from electrochemistry literature when the coefficient of compositional expansion is set to zero, i.e. when there is no coupling between electrochemical and mechanical fields. For the case of non-zero coefficient of compositional expansion, extensive numerical results are presented which show that there is a significant interaction between mechanical stresses and defect distribution.